High voltage power conversion between DC and AC are known in the art for a variety of different applications. One such application is related to HVDC (High Voltage DC).
The concept Modular Multilevel Converter (M2C) denotes a class of Voltage Source Converter (VSC). The M2C comprises a number of converter cells, each comprising switching elements and an energy storage element.
Various types of switching elements can be used, including various types of transistors such as IGBTs (insulated-gate bipolar transistors) and various types of thyristors such as IGCTs (Integrated Gate-Commutated Thyristors). Gate units are provided to control the switching of the switching elements. However, the gate units consume power, which can be significant depending on the type of switching element used.
In the prior art, power electronic converters are used to transform DC power from the converter cell to a DC power suitable for powering the gate units. Such a power electronic converter should transform the voltage from kilo-volts (e.g. 2.6 kV) to a voltage suitable for gate units, e.g. 36V. The power converter with very low gain has very low duty ratio and the peak current through the switching elements may also be one of the limiting factor. Hence, designing such a very low gain DC-DC converter with high power requirement is challenging.